metadata: Set a default empty implementation for buildId()
metadata: Set a default empty implementation for buildId()

Makes flow happy

cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,cozy-labs/cozy-desktop,nono/cozy-desktop,cozy-labs/cozy-desktop,nono/cozy-desktop,nono/cozy-desktop,nono/cozy-desktop